Chapter 16: Problem 8
Sketch graphs of (a) \(y=\operatorname{cosech} x\) and (b) \(y=\operatorname{sech} x\) from \(x=-4\) to \(x=4\), and, from the graphs, determine whether they are odd or even functions.
Short Answer
Expert verified
\(y=\operatorname{cosech} x\) is odd, and \(y=\operatorname{sech} x\) is even.
Step by step solution
01
Understand the Hyperbolic Functions
Before sketching the graphs, we need to understand the given functions. The hyperbolic cosecant, \(y = \operatorname{cosech} x\), is defined as \(y = \frac{1}{\sinh x}\). The hyperbolic secant, \(y = \operatorname{sech} x\), is defined as \(y = \frac{1}{\cosh x}\). Recall that \(\sinh x = \frac{e^x - e^{-x}}{2}\) and \(\cosh x = \frac{e^x + e^{-x}}{2}\).
02
Determine the Domain and Properties of the Functions
The function \(y = \operatorname{cosech} x\) is undefined at \(x = 0\) because \(\sinh 0 = 0\). The function \(y = \operatorname{sech} x \) is defined for all real \(x\) because \(\cosh x > 0\) for any real number. \(\operatorname{cosech} x\) is an odd function \(\operatorname{cosech}(-x) = -\operatorname{cosech}(x)\), and \(\operatorname{sech} x\) is an even function \(\operatorname{sech}(-x) = \operatorname{sech}(x)\).
03
Sketch the Graph of \(y=\operatorname{cosech} x\)
Plot the hyperbolic cosecant, \(y = \operatorname{cosech} x\), which approaches zero from both sides of \(x = 0\) but never touches \(x = 0\). The graph is symmetric with respect to the origin, resembling a curve that falls into asymptotes at \(x = 0\) as \(x\) approaches 0 from either side. Points such as \((1, \operatorname{cosech} 1)\) can be calculated for more accuracy.
04
Sketch the Graph of \(y=\operatorname{sech} x\)
Plot the hyperbolic secant, \(y = \operatorname{sech} x\), which reaches a value of 1 at \(x = 0\) and tends towards zero as \(x\) moves away from zero. The graph is symmetric about the y-axis and appears U-shaped, with a central peak and tails approaching the x-axis. Points like \((1, \operatorname{sech} 1)\) can add accuracy.
05
Determine Odd or Even Nature from Graphs
Since the graph of \( y = \operatorname{cosech} x \) is symmetric about the origin, it is an odd function. The graph of \(y = \operatorname{sech} x\) is symmetric about the y-axis, confirming it is an even function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cosech Function
The hyperbolic cosecant function, denoted as \(y = \operatorname{cosech} x\), is the reciprocal of the hyperbolic sine function \(\sinh x\). This means it is defined as \(y = \frac{1}{\sinh x}\).
\(\cosech x\) is undefined at \(x = 0\) because \(\sinh 0 = 0\), making the expression division by zero, which in mathematics is undefined.
When plotting \(\operatorname{cosech} x\), the graph will show the values approaching zero as \(x\) approaches zero from either direction, but it never actually reaches or crosses the axis.
Such behavior indicates asymptotes at \(x = 0\), which are lines that the graph gets infinitely close to but never touches.
The key points for graphing would involve calculating values at several points, such as \(\operatorname{cosech}(1)\), for better accuracy in the depicted graph.
\(\cosech x\) is undefined at \(x = 0\) because \(\sinh 0 = 0\), making the expression division by zero, which in mathematics is undefined.
When plotting \(\operatorname{cosech} x\), the graph will show the values approaching zero as \(x\) approaches zero from either direction, but it never actually reaches or crosses the axis.
Such behavior indicates asymptotes at \(x = 0\), which are lines that the graph gets infinitely close to but never touches.
The key points for graphing would involve calculating values at several points, such as \(\operatorname{cosech}(1)\), for better accuracy in the depicted graph.
Sech Function
The hyperbolic secant function, represented as \(y = \operatorname{sech} x\), is the reciprocal of the hyperbolic cosine function \(\cosh x\).
This results in the formula \(y = \frac{1}{\cosh x}\). Unlike some hyperbolic functions, \(\cosh x\) does not yield zero for any real value, ensuring \(\operatorname{sech} x\) is defined for all real \(x\).
When plotting \(\operatorname{sech} x\), it peaks at \(x = 0\) where \(y\) reaches a maximum value of 1. As \(x\) deviates from zero, the function value diminishes towards zero, creating a distinct U-shaped curve.
This reflective curve around the y-axis mirrors more traditional trigonometric secant function behavior in this miraculous world of hyperbolics.
This results in the formula \(y = \frac{1}{\cosh x}\). Unlike some hyperbolic functions, \(\cosh x\) does not yield zero for any real value, ensuring \(\operatorname{sech} x\) is defined for all real \(x\).
When plotting \(\operatorname{sech} x\), it peaks at \(x = 0\) where \(y\) reaches a maximum value of 1. As \(x\) deviates from zero, the function value diminishes towards zero, creating a distinct U-shaped curve.
This reflective curve around the y-axis mirrors more traditional trigonometric secant function behavior in this miraculous world of hyperbolics.
Even and Odd Functions
Functions can be categorized based on symmetry:
- **Even functions** satisfy \(f(-x) = f(x)\), showing symmetry around the y-axis.
- **Odd functions** fulfill \(f(-x) = -f(x)\), featuring symmetry around the origin.
The \(\operatorname{sech} x\) function, being an even function, showcases beautiful y-axis symmetry; meaning flipping it horizontally about the y-axis leaves the function unaltered.
Conversely, \(\operatorname{cosech} x\) is an odd function, displaying perfect symmetry about the origin, akin to a reflection through it.
With these characteristics, identifying function nature becomes a visual and analytical delight, bringing clarity to otherwise "functionally" obscure graphs.
- **Even functions** satisfy \(f(-x) = f(x)\), showing symmetry around the y-axis.
- **Odd functions** fulfill \(f(-x) = -f(x)\), featuring symmetry around the origin.
The \(\operatorname{sech} x\) function, being an even function, showcases beautiful y-axis symmetry; meaning flipping it horizontally about the y-axis leaves the function unaltered.
Conversely, \(\operatorname{cosech} x\) is an odd function, displaying perfect symmetry about the origin, akin to a reflection through it.
With these characteristics, identifying function nature becomes a visual and analytical delight, bringing clarity to otherwise "functionally" obscure graphs.
Graph Sketching
Sketching graphs, especially those of hyperbolic functions like \(\operatorname{cosech} x\) and \(\operatorname{sech} x\), enhances understanding of their behavior.
To begin with, noting important features such as maximum, minimum points, and potential asymptotes is crucial.
**Steps for Sketching:**
- **Identify Key Points**: Know values at prominent points like \(x = 0, 1, -1\).
- **Understand Symmetry**: Utilize whether functions are even or odd.
- **Draw Asymptotes**: For \(\operatorname{cosech} x\), acknowledge undefined \(x = 0\) zone.
- **Shape Analysis**: Recognize U-shape of \(\operatorname{sech} x\) and asymptote-reaching curves of \(\operatorname{cosech} x\).
These steps ensure the sketch mirrors mathematical truths accurately.
To begin with, noting important features such as maximum, minimum points, and potential asymptotes is crucial.
**Steps for Sketching:**
- **Identify Key Points**: Know values at prominent points like \(x = 0, 1, -1\).
- **Understand Symmetry**: Utilize whether functions are even or odd.
- **Draw Asymptotes**: For \(\operatorname{cosech} x\), acknowledge undefined \(x = 0\) zone.
- **Shape Analysis**: Recognize U-shape of \(\operatorname{sech} x\) and asymptote-reaching curves of \(\operatorname{cosech} x\).
These steps ensure the sketch mirrors mathematical truths accurately.
Function Properties
Hyperbolic functions hold properties akin to trigonometric siblings, yet portray unique traits.
Both \(\operatorname{cosech} x\) and \(\operatorname{sech} x\) manifest these identities, being inverse hyperbolic functions, having significance in mathematical places.
**Specific Property Highlights:**
- **Domain and Range**: \(\operatorname{cosech} x\) undefined \(x = 0\) versus \(\operatorname{sech} x\) domain \((-\infty, \infty)\).
- **Symmetry Representations**: Illustrated by even-ness and odd-ness.
- **Applications**: Key roles in calculus, physics fields such as wave motion.
These properties assist in delving into vast enforced applications inherent to hyperbolic functions, engaging deeper mathematical allure.
Both \(\operatorname{cosech} x\) and \(\operatorname{sech} x\) manifest these identities, being inverse hyperbolic functions, having significance in mathematical places.
**Specific Property Highlights:**
- **Domain and Range**: \(\operatorname{cosech} x\) undefined \(x = 0\) versus \(\operatorname{sech} x\) domain \((-\infty, \infty)\).
- **Symmetry Representations**: Illustrated by even-ness and odd-ness.
- **Applications**: Key roles in calculus, physics fields such as wave motion.
These properties assist in delving into vast enforced applications inherent to hyperbolic functions, engaging deeper mathematical allure.